I recently finished (mostly) a cuben tarp and used small pieces of flat carbon for the tieouts. 1/2" long pieces of flat carbon are taped into the edges of the tarp with three 10" long, 1/2" wide pieces of cuben tape wrapped over the edge to distribute the pull, placed at different angles to the direction of pull. A hole is drilled into the carbon to tie to (after all the taping is done). No sewing.
This method was inspired by tieout method developed for polycro tarps using nylon washers, mentioned/started at http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=59450&disable_pagination=1
I'll post some details for the construction of this tarp soon, probably in the next week.